Book/Dissertation / PhD Thesis

FZJ-2017-00955

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Entwicklung selbstheilender Wärmedämmschichten

Koch, D. S. (Corresponding author)FZJ*

2016
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-95806-201-6

Please use a persistent id in citations: http://hdl.handle.net/2128/13650

Abstract: The presented work is dealing with the manufacturing of self-healing thermal barrier coatings by atmospheric plasma spraying that are applicable in high temperature processes with thermal loading. The turbine blades of gas turbines for example, experience thermal stresses that are induced into the thermal barrier coatings and can cause crack development. After a certain time these cracks grow and lead to a spallation of the coating. By this, the turbine blade would not be protected any more. With the integration of a self-healing process, the time between maintenances can be extended to save operational costs. The basic idea to realize such self-healing coatings is the integration of MoSi$_{2}$ as self-healing particles. The oxidation of MoSi$_{2}$ leads to the formation of SiO$_{2}$ that can infiltrate cracks and seals them. This can prevent the spallation of the coating. The presented work was performed within a project named SAMBA (self-healing thermal barrier coatings) that was funded by the European Union. The first step in the production of a self-healing thermal barrier coating was the integration of MoSi$_{2}$ particles into a coating. Yttria stabilized zirconia (YSZ) was used as coating matrix since this is the state of the art material. Due to a decomposition of the MoSi$_{2}$ when spraying it at conditions that are needed to produce coatings made out of YSZ, the manufacturing of a homogeneous mixed coating of YSZ and MoSi$_{2}$ from a powder mixture of both materials was not possible. This problem was solved by using a second injection point located at a distance from the plasma-torch-exit. Nevertheless the coatings made out of YSZ and pure MoSi$_{2}$ were not suitable to work as a self-healing thermal barrier coating due to the fact that the oxidation of MoSi$_{2}$ was not controlled. The volume expansion caused by the formation of SiO$_{2}$ induces stresses into the coating that lead to a failure and the spallation of the coating. The second step in the development was to encapsulate the MoSi$_{2}$ particles with Al$_{2}$O$_{3}$, as this encapsulation was supposed to work as a protection against a premature oxidation of the MoSi$_{2}$. As the spraying process leads to a deformation of the particles during deposition on the substrate, a pre-encapsulation of the powder would be destroyed. Because of this, the encapsulation has to be formed in-situ within the coating. Several coatings were produced using Al doped MoSi$_{2}$ to integrate it into the YSZ coatings. These coatings were heat treated and by this several requirements were determined that need to be fulfilled in order to enable the self-healing process. Coatings that have been produced using spraying parameters, that enable the fulfillment of these requirements, and these coatings resulted in an improvement of the lifetime of the coatings compared to standard YSZ coatings. Within the SAMBA project further analysis and investigations will be performed to be able to judge on the self-healing abilities of coatings produced by the procedures described in this work.

Note: Universität Bochum, Diss., 2016

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Contributing Institute(s):

1. Werkstoffsynthese und Herstellungsverfahren (IEK-1)

Research Program(s):

1. 113 - Methods and Concepts for Material Development (POF3-113) (POF3-113)
2. HITEC - Helmholtz Interdisciplinary Doctoral Training in Energy and Climate Research (HITEC) (HITEC-20170406) (HITEC-20170406)

Appears in the scientific report 2016

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Database coverage:
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